Oils and fats resulting from extraction are named crude due to the fact that they contain small quantities of compounds other than triacylglycerol esters. In the refinery these crude oils and fats are processed so as to remove undesirable substances in order to produce useful products.
The substances removed include free fatty acids, phospholipids, carbohydrates, proteins and their degradation products, water, pigments (carotenoids and chlorophyly mainly) and oxidized fat products. Thus the need for a number of commercial refining processes conceived to remove these substances is apparent.
There are two types of refining processes in common use today: physical and chemical refining. Similar steps are taken in both processes but with distinct objectives. Generally vegetable oils and meat fats are refined chemically, but certain vegetable oils, like coconut and palm, are physically refined for it is more economical. The choice of process relies normally on the convenience and the cost of the process.
It must be stressed that in both of these processes rather high temperatures are attained, a fact that might entail an appreciable degree of cis-trans isomerisation of polyunsaturate components, which is nutritionally objectionable. On the other hand a relatively large quantity of effluent originates at the refinery.
Considerations such as these actively concurr to make the refinery area prone to innovative practices which are presently the object of much R&D. Two examples of this are lower temperature processing making extensive use of adsorption processes which may come to be preferred, and the recycling and/or reuse of adsorbents.
b) Neutralization (chemical processing)